Therapeutic medical compression garments are used on a relatively wide scale to assist in the management of venous and lymphatic disorders. The purpose of such stockings is to counter the effects of elevated pressures internally within the human anatomy caused by gravity or disease processes. They may also be applied to inactive, bedridden individuals to help prevent a thromboembolic event. The purpose of such garments in this case is to maintain directional flow of blood, thereby helping to reduce the risk of thrombus formation in the superficial and deep veins.
More specifically, therapeutic stockings typically have a rather precisely defined and controlled pressure profile to effect a predetermined compression of the interstitium of the leg. The custom Venous Pressure Gradient Stocking was developed by Conrad Jobst, a sufferer of venous disease. Mr. Jobst found relief from his problem while standing in a swimming pool. Mr. Jobst reasoned that the water pressure in the pool, which increases with depth, cancelled out the internal pressure in the veins of his leg. Jobst and others identified a need to apply relatively large compression force in proximity to the ankle.
Therapeutic medical gradient compression garments are designed to provide sufficient external circumferential counter pressure to maintain the venous and lymphatic pressures at a more normal level in the extremity, thus assisting the movement of venous blood and lymph from the extremity. Another important effect of compression is the reduction of venous volume. Reduction of venous volume leads to an increase of venous flow velocity. While the exact mechanism of action of gradient compression therapy remains unknown, improvements in skin and subcutaneous tissue microcirculatory hemodynamics may contribute to the benefits of compression therapy. The direct effect of compression on subcutaneous pressure is a plausible mechanism. Edema reduction and edema prevention is the goal in patients with chronic venous insufficiency, lymphedema, and other edema causing conditions. Subcutaneous pressures increase with elastic compression. This rise in subcutaneous tissue pressure acts to counter transcapillary Starling forces, which favor leakage of fluid out of the capillary.
There are a variety of therapeutic medical gradient compression garments on the market today. For example, stockings of various descriptions have been proposed. Unfortunately, therapeutic stockings have a tendency to slip down the leg of the wearer, thereby detracting from the benefits of the stocking. An example of a therapeutic stocking is described in U.S. Pat. No. 3,975,929 to Fregeolle which describes a thigh length anti-embolism stocking made with alternating courses of covered spandex yarn on a circular hosiery knitting machine. The stocking described in Fregeolle shows a turned welt around a portion of the top of the stocking and a narrow elastic band stitched to the upper portion of the stocking. The inner face of the elastic band is provided with beads or rows of frictional gripping material that aid in supporting the upper end of the stocking on the leg of the wearer by frictionally engaging the leg.
Another example of a therapeutic stocking is described in U.S. Pat. No. 3,874,001 to Patience, et al., which discloses a full length stocking having a foot and leg portion made from circumferential elastic. A narrow band of non-slip elastomeric webbing material is sewn to the upper end of the leg portion by over stitching. The particular stitching used is said to provide for adequate “play” in the stitching to insure the deformation of the stocking as it is worn.
In U.S. Pat. No. 3,983,870 to Herbert, et al. there is disclosed a slip-resistant support for limbs, especially a medical stocking. Herbert, et al. address the slip problem by coating 20 to 30 percent of the leg portion of the outer parts of the inner surface of the knitted thread. The inner surface is coated with a non-adhesive, non-continuous, relatively soft elastomeric polymeric material with a high coefficient of friction to skin so as to provide a nonocclusive slip resistant surface capable of maintaining the support in place on the limb of the body.
Another type of anti-embolism stocking is disclosed in U.S. Pat. No. 3,728,875 to Hartigan, et al. This stocking is knit on a circular hosiery knitting machine and the upper portion is slit downwardly in a walewise direction and a wedge shaped insert of soft elastic fabric is sewn into the slit to increase the circumference of the upper end of the stocking. In stockings of this type the sewing of the wedge increases the cost of production. The insert is formed of a different compressive fabric than the remaining portion of the upper end of the stocking so that the portion of the leg covered by the insert does not receive the same compressive force as applied to the remaining portion of the leg of the wearer. The stocking also has a partial round of elastic retention band made with a corrugated anti-slip inner surface of urethane elastomer sewn to the upper narrow welt of the stocking proper, projecting above the stocking welt so that its top forms a continuous line with the top of the insert.
Although strides have been made in improving the anti-slipping properties of anti-embolism garments, application of elastomeric bands requires a separate manual sewing operation, which increases the costs of production. Thus, there remains a need for an effective, inexpensive therapeutic medical compression garment that will resist slipping down the leg of the wearer.